1. Field of the Invention
The invention relates to a record carrier comprising substantially parallel tracks having first variations of a first physical parameter of the track, the first variations representing information recorded on the record carrier, the information being recoverable by a controllable type of data processing; and second variations of a second physical parameter of the track, a modulation pattern of the second variations representing a code for controlling said type of data processing.
The invention further relates to a method of recording information on a record carrier, wherein the record carrier is provided with substantially parallel tracks, the method comprising encoding the information in first variations of a first physical parameter of the track, the information being recoverable by a controllable type of data processing; and encoding a code for controlling said type of data processing in a modulation pattern of second variations of a second physical parameter of the track.
The invention further relates to a playback device for recovering information from the record carrier, the device comprising reading means for generating a read signal in dependence on the first variations, and demodulation means for retrieving the code from the modulation pattern of the second variations, and data processing means for processing the read signal for recovering the information in dependence on the code.
2. Description of the Related Art
A system for recording information comprising a record carrier, a recording method and a playback device, is known from U.S. Pat. No. 5,724,327. The record carrier comprises tracks in which the information is represented in a predefined manner by optically readable marks of first variations of a first physical parameter, such as the reflectivity of the scanned surface. The track further has second variations of a second physical parameter, such as a periodic excursion of the track in a transverse direction (further denoted as wobble), a variation in depth, shape or width of the marks. The second variations are modulated and the modulation pattern represents a code which is used for recovering the information, e.g., a de-scramble code for recovering information stored as scrambled information. Said code may constitute a medium mark usable in a system for copy protection, because the track wobble cannot be copied to a recordable disc on standard recording equipment. The playback device comprises reading means for reading the optical marks and demodulation means for retrieving the code from the modulation of the second variations. The player and information carrier form a system for controlled information reproduction. For this purpose, the player comprises data processing means for reproducing the information in dependence on the retrieved code. If the information is copied on a writable information carrier, the information of this copy will not be reproduced by said player, because during the copying process, only the information represented by the first variations is written to the writable information carrier. The copied information carrier does not contain the code, as the second variations cannot be produced by standard recording devices. However, the known system cannot be applied to an existing high-density record carrier, like DVD, because such high-density record carrier systems have tight tolerances on the parameters of the track and the required modulation of a second physical parameter would disrupt the reading of the marks and cause errors in the retrieved information.